A new study suggests that people who are more generous have a larger temporoparietal junction, a region located on the right side of the brain.

Swiss researchers who studied 30 volunteers found that ranked the altruism of each person by detecting their ‘cutoff’ – the maximum they were prepared to give to others.

“We were very surprised by how strong the relationship was between altruistic decision and what we found out about their brain structure,” said co-author Dr. Yosuke Morishima.

“These tendencies don’t change in the short-term – nice people don’t become mean overnight – and this area may explain the variation between individuals.”

According to the study published in the journal Neuron, although a ‘baseline level’ of altruism is hardwired into our brains, the decisions we make are affected by lots of other factors like the context and potential cost to ourselves.

Behavior researcher Professor Ernst Fehr of the University of Zurich, this is the first biological explanation for people’s altruism levels, when tend to remain stable during their lives.

Previous studies that looked at unstable factors such as gender, level of income, wealth or educational achievements could not link any of these traits to altruism.